Tentatively grabbing this for next week. Likely to get punted though :)

Passing over to Jan :)

For example code, look at PopularSitesInternalsUI and PopularSitesInternalsMessageHandler.

I would like to get the full list of snippets displayed during next week.

Could please also consider adding a button to clear the list of discarded snippets? If I clear all snippets for tests, I then have to wait for a while before I can get anything to show up again. The list of discarded snippets is kept here: https://code.google.com/p/chromium/codesearch#chromium/src/components/ntp_snippets/ntp_snippets_service.h&q=discarded%20f:ntp_snippets&sq=package:chromium&type=cs&l=157

Sure, Nicolas!

I have the internal page with most of the desired features. I upload the CL for review early next week.

I am experiencing some weird bugs in chrome, trying to understand / rule out these are my bugs. Slows down the progress substantially.

In the meantime, I have polished the code and gone through one round of code review (thanks, Marc!).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749

commit 3ccb46d44ee5a1a3a5cee851792fb01b8ef56749
Author: jkrcal <jkrcal@chromium.org>
Date: Mon Apr 18 15:59:06 2016

chrome://snippets-internals page for debugging NTP snippets.

Displays a list of NTP snippets and discarded snippets with all details
(as obtained from the ChromeReader servers). It also shows the list of
hosts by the SuggestionService to which the snippets are restricted.

The page allows to clear the list of snippets / discarded snippets as
well as to fetch new snippets from user-specified hosts.

BUG= 597566 
NOPRESUBMIT=true

(the presubmit check fails on javascript arrow function, see https://bugs.chromium.org/p/chromium/issues/detail?id=567770#c8)

Review URL: https://codereview.chromium.org/1883523002

Cr-Commit-Position: refs/heads/master@{#387919}

[modify] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/browser/browser_resources.grd
[add] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/browser/resources/snippets_internals.css
[add] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/browser/resources/snippets_internals.html
[add] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/browser/resources/snippets_internals.js
[modify] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc
[add] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/browser/ui/webui/snippets_internals_message_handler.cc
[add] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/browser/ui/webui/snippets_internals_message_handler.h
[add] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/browser/ui/webui/snippets_internals_ui.cc
[add] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/browser/ui/webui/snippets_internals_ui.h
[modify] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/chrome_browser_ui.gypi
[modify] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/common/url_constants.cc
[modify] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/chrome/common/url_constants.h
[modify] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/components/ntp_snippets/ntp_snippets_service.cc
[modify] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/components/ntp_snippets/ntp_snippets_service.h
[modify] https://crrev.com/3ccb46d44ee5a1a3a5cee851792fb01b8ef56749/components/ntp_snippets/ntp_snippets_service_unittest.cc

One optional piece from the original specification is not implemented, yet:

- An "event log" that shows when snippets were added/discarded/expired etc

We agreed with Marc to implement this and any further features only if requested.